The invention relates to plasmatrons for spectroanalysis applications and the like, and more particularly to stabilized plasmatrons having facilities for introducing additives into the plasma stream developed thereby.
In known types of plasmatrons of this type, an arc is established between spaced cathode and anode electrodes, and an ionizable gas such as argon is introduced into the arc discharge space to define a plasma stream. In one advantageous embodiment, metal plates insulated from the cathode and anode are situated between the cathode and the anode for stabilizing the plasma stream to facilitate a mixing of the plasma with an additive before the stream leaves the device.
The disadvantage of such arrangement, in which the plasma stream is directed from the anode to the cathode, is that extremely high temperatures are generated at the cathode where the beam emerges from the device, thereby leading to frequent failures and breakdowns of the equipment. Additionally, such high temperatures exert a severely limiting effect on the quantity of additives which may be mixed in the plasma stream, and in general limit the material state of the additives to fluid form.